The present invention relates generally to improvements in access opening plug devices and it relates more particularly to an improved closure device or bushing device for use in the walls of electrical fittings such as junction boxes, switch boxes and the walls of similar enclosures and the like.
In many electrical wall and enclosure structures, such as switch and junction boxes which receive electrical conduit and the like, it is frequently highly desirable or necessary to plug an opening in the enclosure wall either to close the openings or provide it with a bushing to facilitate the non-abrasive passage of an electrical cable. The cables are often snakes through the conduit and bent in the junction box. These openings are generally circular and are produced with large tolerances, so that there is a great variation in the diameter of the opening from the nominal diameter. Accordingly, any plug device to be satisfactory, whether it be a closure device or a bushing device, must accommodate to a wide range of sizes while permitting easy application of the plug device and its firm engagement of the receiving opening. There have been many forms of opening plug devices available and proposed but these possess numerous drawbacks and disadvantages. They are often unreliable and difficult to apply, accommodate limited variations in diameter of the hole, are expensive and are of little versatility and adaptability.